Southern Tobacco Flea Beetle Epitrix fasciata Blatchley Coleoptera Chrysomelidae

Natural History

Distribution. Tobacco flea beetle, Epitrix hirtipennis (Melsheimer), is distributed widely in the United States. It is found most commonly in the southeast, but also as far north as Maryland and Michigan, and west to southern Colorado and California. It is infrequent in the northwest and Great Plains, but apparently occurs in Hawaii and Mexico. In Canada, it is known from Ontario and Quebec.

Southern tobacco flea beetle, Epitrix fasciata Blatch-ley, has limited distribution in the United States, and is known only along the Gulf Coast, from Florida to Texas. It occurs widely in Central America and the Caribbean, and as far south as Argentina.

Host Plants. Tobacco flea beetle adults feed readily upon tobacco and other plants in the family Solana-ceae, but sometimes attack other plants as well. Vegetable crops most frequently attacked are eggplant, potato, and tomato, but cabbage, cowpea, pepper, snap beans, and turnip are consumed occasionally. Weeds commonly serving as hosts are nightshade, Solanum spp.; jimsonweed, Datura stramonium; groundcherry, Physalis heterophylla; pokeweed, Phytolacca americana; burdock, Arctium minus; cocklebur, Xanthium spp.; and many others. The larvae develop successfully on many solanaceous plants, but do not survive on non-solanaceous plants. In studies conducted in Virginia, tobacco, potato, and jimsonweed were particularly good hosts for larvae (Glass, 1943).

The little information available on southern tobacco flea beetle suggests that the host range is nearly identical to that of tobacco flea beetle (White and Barber, 1974).

Natural Enemies. Tobacco flea beetle is preyed upon to a limited extent by general predators such as bigeyed bug, Geocoris punctipes (Say) (Hemiptera: Lygaeidae) (Dominick, 1943). The principal parasitoid seems to be Microctonus epitricis (Vierick) (Hymenop-tera: Braconidae), which causes parasitism rates of up to 25% (Dominick and Wene, 1941). This parasitoid also attacks southern tobacco flea beetle.

A nematode, Howardula dominicki Elsey (Nematoda: Allantonematidae), parasitizes up to 70% of larvae and 50% of adults of tobacco flea beetle. Host larvae are killed, and adult females are made sterile by the nematodes. Male beetles are important in nematode dissemination. The biology of this nematode was provided by Elsey and Pitts (1976), and Elsey (1977b,c).

Life Cycle and Description. The number of annual generations of tobacco flea beetle varies, with three reported from Kentucky, 3-4 in Virginia, and 4-5 from Florida. In Kentucky, Jewett (1926) observed first generation adults, resulting from reproduction by overwintering beetles, in mid-June. This was followed by a second generation in late July, and a third in September. Not all insects undergo the third generation, however, some commence overwintering after only two generations. In Florida, Chamberlin et al. (1924) reported four well-defined generations, but there may be additional generations. Overwintering occurs in the adult stage, under plant debris, and often in weedy or wooded areas adjacent to crop fields. In the south, the beetles may remain active throughout the winter.

  1. Tobacco flea beetle eggs are elongate and slightly pointed at one end. Initially, the egg is white, but gradually changes to lemon yellow as it matures. The egg measures about 0.41 mm (range 0.36-
  2. 48 mm) long and 0.18 mm (range 0.16-0.26 mm) wide. Eggs are deposited in the soil near the base of the host plant, frequently in clusters of 5-6 eggs. Moist areas are preferred for oviposition. Eggs hatch in 6-8 days. Overwintering females deposit, on an average, 2.2 eggs per day, and total production is estimated at about 200 eggs per female. Later generations seem to live for a shorter period of time, and the number of eggs produced per female is about 100.
  3. The larvae have three instars, and grow in size from less than 1 mm at hatching to about 4.2 mm at maturity. The larva is whitish, except for the head, which is yellow or yellow-brown. The terminal abdominal segment bears an anal proleg. Larvae feed principally on the fine roots of solanaceous plants, but occasionally larger roots are girdled or tunneled. Except when the soil is very dry, larvae also feed near the soil surface. Larval development time averages 1620 days, depending on generation and weather. Jewett (1926) determined the duration of the three instars to be 4.6, 3.9, and 5.4 days, respectively. Average head capsule width measurements for the instars is 0.12, 0.17, and 0.21mm, respectively (Martin and Herzog, 1987). Larvae are cannibalistic.
  4. At maturity, larvae prepare a small cell in the soil and after 1-2 days transform into the pupal stage. The pupa closely resembles the adult in form, measures about 1.75 mm long, and is whitish. Pupation occurs within the upper 1-3 cm of soil, and lasts 4-5 days.
  5. The adults measure only about 1.4-2.2 mm long. They are reddish-yellow, with a brown abdomen and a brown irregular transverse patch or band crossing, or nearly crossing, the yellow elytra. The legs are also reddish-yellow except for the darker femora of the hind legs. The hind femora are enlarged. As is the case with all Epitrix beetles, the entire body bears a coat of short hairs. Adults live for several weeks, resulting in overlapping generations and almost continuous egg production. The pre-oviposition period is 2-3 weeks.

Tobacco flea beetle, E. hirtipennis, and southern tobacco flea beetle, E. fasciata, are quite similar in appearance. E. hirtipennis is slightly larger and narrower, measuring 1.6-2.2 mm long and 1.9-2.0 times as long as wide. E. fasciata is 1.4-1.7 mm long and 1.7-1.8 times as long as wide. There is a broad transverse band across the elytra of both species, but although it is continuous in E. hirtipennis it is generally interrupted in E. fasciata (White and Barber, 1974).

The biology of the tobacco flea beetle was given by Metcalf and Underhill (1919), Jewett (1926), and Dominick (1943). Simple rearing techniques were pro-

Epitrix Fasciata
Adult tobacco flea beetle.

vided by Jewett (1926), and Martin and Herzog (1987). Most research focuses on the relationship of tobacco flea beetle with tobacco, despite its common association with vegetable crops. The biology of southern tobacco flea beetle is poorly known, but is presumed similar to tobacco flea beetle. (See color figure 115.)

Damage

The nature of damage caused by these species is typical of flea beetle injury. Adults eat small holes partly or completely through the leaves, usually feeding from the underside. In the former instance, the adjacent remaining tissue usually dies and drops from the plant, leaving a somewhat circular hole. Foliage, especially of young plants, may be riddled with these small holes. In extreme cases, only the veins may remain, seriously disrupting the physiology of the plant. The result is usually stunted plants, although seedlings sometimes are killed. Feeding by as few as five beetles for a three-week period early in the life of a plant may result in significant yield reduction in tobacco, and presumably other crops (Semtner, 1984a). The beetles are more active and damaging during warm and sunny weather. They often feed selectively on shaded, or lower sections of the plant.

The larvae feed on the roots, particularly the rootlets. Even a single larva feeding on a germinating seedling may cause enough damage leading to death of the plant. The discoloration of the seedling stem base, wilting, and rapid death of the plant caused by larval feeding greatly resembles seedling "damping off'' due to plant parasitic fungi (Gentile and Stoner, 1968a).

Management

  1. Various approaches for monitoring abundance of tobacco flea beetle have been investigated. Soil cores can be collected for estimation of larval, pupal, and adult numbers. Larvae can be separated from soil with heat extraction by using Berlese funnels. Pupae, being nonmotile, must be separated by flotation or visual examination. Soil samples can be held in containers for adult emergence, but ield emergence traps are more usual. Duke and Lambert (1987) recommended sample sizes of about 50, 12, and 30 soil cores for these three life stages, respectively. Adults can also be monitored with colored sticky traps; yellow is the most attractive color (Dominick, 1971).
  2. Foliar and soil-applied insecticides are commonly used for tobacco flea beetle suppression. Systemic insecticides are particularly useful for the young and rapidly growing seedlings because the leaf tissue is expanding very rapidly and multiple applications of non-systemic material would be necessary to protect the foliage from adult feeding damage.

Cultural Practices. Modification in planting date has been examined for reduction in flea beetle impact, but without much success. Late-planted crops may escape the attack of overwintering beetles, but plants then are relatively small and susceptible to injury by first brood adults (Semtner, 1984b). Also, crop yields or crop value are often adversely affected by late planting, which can outweigh the benefits of avoiding flea beetle injury.

Host-plant nutrition affects flea beetles differently, depending on the nutrient (Semtner et al., 1980). High nitrogen levels sometimes seem to affect flea beetles, but the pattern is not consistent. Plants with higher levels of phosphorus are less preferred by beetles, whereas higher levels of potassium favor adult abundance.

Among other methods of cultural control that have been studied are row covers, burning, and host plant resistance. Row covers work quite well for most pests, but as the beetles may overwinter in the ield, they can emerge under the protective covering. Thus, this practice has limitations if the ield was infested previously. Burning of crop residue and ield edges, where overwintering may occur, may kill some beetles, but it is no longer recommended routinely because the bene-its are slight. Host-plant resistance has been sought for some crops, such as Lycopersicon spp. (tomato and its relatives), but without much success (Gentile and Stoner, 1968b). Although some selections had glandular hairs that reduced feeding by adults, even wild species were susceptible to larvae.

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  • Nicole
    Where do clypastraea fasciata beetle live?
    6 years ago

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